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The Detached Dust Shell around the Massive Star HD 179821
The Astrophysical Journal
|October 20, 1999
Summary
HD 179821, a G-type supergiant, has a detached dust shell. Mass loss slowed dramatically ~1800 years ago, suggesting radiation pressure may drive its asymmetric circumstellar winds.
Area of Science:
- Astronomy and Astrophysics
- Stellar Evolution
- Circumstellar Environments
Background:
- HD 179821 (RAFGL 2343) is a G-type supergiant star.
- The star possesses a detached dust shell, indicating a complex mass-loss history.
Purpose of the Study:
- To resolve the mid-infrared emission from HD 179821 and its detached dust shell.
- To investigate the characteristics of the star's mass-loss history and circumstellar wind.
Main Methods:
- Utilized the Keck I telescope to observe emission at three mid-infrared wavelengths.
- Analyzed the morphology and dimensions of the detached dust shell.
Main Results:
- The dust shell has an inner diameter of approximately 3.3 arcseconds (3.0x10^17 cm).
- Mass loss rate was estimated at ~4x10^-4 M☉ yr⁻¹ until ~1800 years ago, then slowed significantly.
- The star's position within the shell suggests asymmetric outflow velocities, potentially driven by radiation pressure.
Conclusions:
- The mass loss may have been driven by radiation pressure, with M_dot * V_infinity ~ L*/c.
- Asymmetric circumstellar winds can be characterized, providing insights into supernova propagation.